Anthracene derivative and light emitting element and light emitting device using the same

ABSTRACT

It is an object of the present invention to provide a luminescent material that has resistance to repeated oxidation reactions. Further, it is an object of the present invention to provide a light-emitting element that is high in luminous efficiency. Further, it is an object of the present invention to provide a light-emitting element that has a long life. An aspect of the present invention is an anthracene derivative represented by a general formula (1). In the general formula (1), R 2  to R 4  and R 7  to R 9  are individually any one of hydrogen, an alkyl group having 1 to 4 carbon atoms, and a group represented by the following structure formula (2), and R 1 , R 5 , R 6 , and R 10  are individually any one of hydrogen and an alkyl group having 1 to 4 carbon atoms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an anthracene derivative, andparticular relates to an anthracene derivative that can be used as amaterial for a light-emitting element.

2. Description of the Related Art

In these years, many of light-emitting elements that are used indisplays and the like have a structure in which a layer including aluminescent material is sandwiched between a pair of electrodes. Inthese light-emitting elements, light is emitted when an exciton formedby recombination of an electron injected from one of the electrodes anda hole injected from the other electrode returns to the ground state.

In the field of light-emitting elements, the structure of a layerincluding a luminescent material, a novel material for forming a layerincluding a luminescent material, or the like has been developed inorder to obtain a light-emitting element that is superior in luminousefficiency and color purity or is able to prevent quenching or the like.

For example, in Patent Document 1, a material that is high in luminousefficiency, has a long life, and is used for an organic EL element isdisclosed.

Now then, in a light-emitting element, current flows between electrodesby transfer of holes or electrons. In this case, a luminescent materialor the like that has holes or electrons received, that is, an oxidizedor reduced luminescent material or the like, sometimes changes to havedifferent properties without returning to the neutral. Further, whensuch change in properties of the luminescent material is accumulated,there is a possibility that characteristics of the light-emittingelement change.

Therefore, development of a luminescent material that is unlikely tochange in properties by oxidation or reduction has been required.

(Patent Document 1) Japanese Patent Application Laid-Open No.2001-131541

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a luminescentmaterial that has resistance to repeated oxidation reactions. Further,it is an object of the present invention to provide a light-emittingelement that is high in luminous efficiency. Further, it is an object ofthe present invention to provide a light-emitting element that has along life.

An aspect of the present invention is an anthracene derivativerepresented by a general formula (1).

In the general formula (1), R² to R⁴ and R⁷ to R⁹ are individually anyone of hydrogen, an alkyl group having 1 to 4 carbon atoms, and a grouprepresented by the following structure formula (2), and R¹, R⁵, R⁶, andR¹⁰ are individually any one of hydrogen and an alkyl group having 1 to4 carbon atoms.

Another aspect of the present invention is an anthracene derivativerepresented by a general formula (3).

In the general formula (3), R¹¹ to R¹⁸ are individually any one ofhydrogen and an alkyl group having 1 to 4 carbon atoms, or R¹¹ and R¹²,R¹³ and R¹⁴, R¹⁵ and R¹⁶, and R¹⁷ and R¹⁸ are individually bonded tofrom an aromatic ring. It is to be noted that the bond of R¹¹ and R¹²,the bond of R¹³ and R¹⁴, the bond of R¹⁵ and R¹⁶, and the bond of R¹⁷and R¹⁸ are independent of one another.

Another aspect of the present invention is an anthracene derivativerepresented by a general formula (4).

In the general formula (4), R²¹ to R²⁸ are individually any one ofhydrogen and an alkyl group having 1 to 4 carbon atoms, or R²¹ and R²²,R²² and R²³, R²⁵ and R²⁶ and R²⁶ and R²⁷ are individually bonded to froman aromatic ring. It is to be noted that the bond of R²¹ and R²², thebond of R²² and R²³, the bond of R²⁵ and R²⁶, and the bond of R²⁶ andR²⁷ are independent of one another.

Another aspect of the present invention is an anthracene derivativerepresented by a general formula (5).

In the general formula (5), Ar¹ and Ar² are individually an aryl grouphaving 6 to 14 carbon atoms. It is to be noted that the aryl group mayhave a substituent, for example, a substituent having 1 to 4 carbonatoms.

Another aspect of the present invention is a light-emitting elementincluding the anthracene derivative represented by any one of thegeneral formulas (1), (3), (4), and (5).

Another aspect of the present invention is a light-emitting device usinga light-emitting element including the anthracene derivative representedby any one of the general formulas (1), (3), (4), and (5).

Another aspect of the present invention is a light-emitting device thathas, in a pixel portion, a light-emitting element including theanthracene derivative represented by any one of the general formulas(1), (3), (4), and (5).

Another aspect of the present invention is an electronic device in whicha light-emitting device using a light-emitting element including theanthracene derivative represented by any one of the general formulas(1), (3), (4), and (5) is mounted.

According to the present invention, a light-emitting element that hasgreat resistance to repeated oxidation reactions can be obtained. Inaddition, a light-emitting element that has little change incharacteristics associated with change in properties of a luminescentmaterial due to repeated oxidation reactions and shows stable lightemission for a long period can be obtained. In addition, alight-emitting element that emits light efficiently can be obtained byusing an anthracene derivative according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a diagram illustrating a light-emitting element according tothe present invention;

FIG. 2 is a diagram illustrating a light-emitting device according tothe present invention;

FIG. 3 is a diagram illustrating a light-emitting device according tothe present invention;

FIG. 4 is a diagram illustrating a circuit included in a light-emittingdevice according to the present invention;

FIG. 5 is a top view of a light-emitting device according to the presentinvention;

FIG. 6 is a diagram illustrating operation per frame for alight-emitting device according to the present invention after sealing;

FIGS. 7A to 7C are cross-sectional views of light-emitting devicesaccording to the present invention;

FIGS. 8A to 8C are diagrams of electronic devices according to thepresent invention;

FIG. 9 is a diagram showing an absorption spectrum of a single film ofan anthracene derivative according to the present invention;

FIG. 10 is a diagram showing an emission spectrum of the single film ofthe anthracene derivative according to the present invention;

FIG. 11 is a diagram showing a measurement result of the anthracenederivative according to the present invention by cyclic voltammetry(CV);

FIG. 12 is a diagram showing current density-luminance characteristicsof a light-emitting element according to the present invention

FIG. 13 is a diagram showing voltage-luminance characteristics of thelight-emitting element according to the present invention;

FIG. 14 is a diagram showing luminance-current efficiencycharacteristics of the light-emitting element according to the presentinvention; and

FIG. 15 is a diagram showing a measurement result of the light-emittingelement according to the present invention by performing an operationalstability test.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

Examples of anthracene derivatives according to the present inventionwill be described.

Anthracene derivatives according to the present invention includeanthracene derivatives represented by structure formulas (6) to (9).

These anthracene derivatives are synthesized in accordance with thefollowing synthesis scheme (a-1) or (a-2).

In the synthesis scheme (a-1), R¹¹ to R¹⁸ are individually any one ofhydrogen and an alkyl group having 1 to 4 carbon atoms, or R¹¹ and R¹²,R¹³ and R¹⁴, R¹⁵ and R¹⁶ and R¹⁷ and R¹⁸ are individually bonded to froman aromatic ring. It is to be noted that the bond of R¹¹ and R¹², thebond of R¹³ and R¹⁴, the bond of R¹⁵ and R¹⁶, and the bond of R¹⁷ andR¹⁸ are independent of one another.

In the synthesis scheme (a-2), R²¹ to R²⁸ are individually any one ofhydrogen and an alkyl group having 1 to 4 carbon atoms, or R²¹ and R²²,R²² and R²³, R²⁵ and R²⁶, and R²⁶ and R²⁷ are individually bonded tofrom an aromatic ring. It is to be noted that the bond of R²¹ and R²²,the bond of R²² and R²³, the bond of R²⁵ and R²⁶, and the bond of R²⁶and R²⁷ are independent of one another.

The above-described anthracene derivatives according to the presentinvention have resistance to the repeated oxidation reactions. Inaddition, the above-described anthracene derivatives according to thepresent invention are able to show blue or bluish luminescence.

Embodiment 2

The structure of a light-emitting element using an anthracene derivativeaccording to the present invention as a luminescent material will bedescribed with reference to FIG. 1.

FIG. 1 shows a light-emitting element that has a light-emitting layer113 between a first electrode 101 and a second electrode 102. In thelight-emitting layer 113, an anthracene derivative represented by anyone of the general formulas (1), (3), (4), and (5) and the structureformulas (6) to (9) according to the present invention is included.

In this light-emitting element, a hole emitted from the first electrode101 and an electron injected from the second electrode 102 arerecombined in the light-emitting layer 113 to bring the anthracenederivative according to the present invention to an excited state. Then,light is emitted when the anthracene derivative according to the presentinvention in the excited state returns to the ground state. As justdescribed, the anthracene derivative according to the present inventionserves as a luminescent material. It is to be noted that the firstelectrode 101 and the second electrode 102 respectively serve as ananode and a cathode in the light-emitting element in the presentembodiment.

Here, the light-emitting layer 113 is not particularly limited. However,it is preferable that the light-emitting layer 113 be a layer in whichthe anthracene derivative according to the present invention is includedso as to be dispersed as a guest material in a layer composed of amaterial that has a larger energy gap than the anthracene derivative.This makes it possible to prevent quenching of luminescence from theanthracene derivative according to the present invention due to aconcentration. It is to be noted that an energy gap indicates an energygap between a LUMO level and a HOMO level.

The material (host material) to be used for dispersing the anthracenederivative according to the present invention is not particularlylimited. However, metal complexes such asbis[2-(2-hydroxyphenyl)-pyridinato]zinc (abbreviation: Znpp₂) andbis[2-(2-hydroxyphenyl)-benzoxazolato]zinc (abbreviation: ZnBOX) arepreferable in addition to an anthracene derivative such as9,10-di(2-naphthyl)-2-tert-butylanthracene (abbreviation: t-BuDNA) and acarbazole derivative such as 4,4′-bis(N-carbazolyl)-biphenyl(abbreviation: CBP).

Although the first electrode 101 is not particularly limited, it ispreferable that the first electrode 101 is formed by using a materialthat has a larger work function when the first electrode 101 functionsas an anode as in the present embodiment. Specifically, in addition toindium tin oxide (ITO), indium tin oxide including silicon oxide, andindium oxide including zinc oxide at 2 to 20%, gold (Au), platinum (Pt),nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe),cobalt (Co), copper (Cu), palladium (Pd), and the like can be used. Thefirst electrode 101 can be formed by, for example, sputtering orevaporation.

In addition, although the second electrode 102 is not particularlylimited, it is preferable that the second electrode 102 is formed byusing a material that has a smaller work function when the secondelectrode 102 functions as a cathode as in the present embodiment.Specifically, aluminum containing an alkali metal or an alkali-earthmetal such as lithium (Li) or magnesium, and the like can be used. Thesecond electrode 102 can be formed by, for example, sputtering orevaporation.

Further, in order to extract emitted light to the outside, it ispreferable that any one or both of the first electrode 101 and thesecond electrode 102 be an electrode composed of a material such asindium tin oxide or an electrode formed to be several to several tens nmin thickness so that visible light can be transmitted.

In addition, a hole transporting layer 112 may be provided between thefirst electrode 101 and the light-emitting layer 113 as shown in FIG. 1.Here, a hole transporting layer is a layer that has a function oftransporting holes injected from the first electrode 101 to thelight-emitting layer 113. By providing the hole transporting layer 112to keep the first electrode 101 away from the light-emitting element 113in this way, quenching of emission due to a metal can be prevented.

The hole transporting layer 112 is not particularly limited, and it ispossible to use a layer formed with the use of, for example, an aromaticamine compound (that is, compound including a bond of a benzenering-nitrogen) such as 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl(abbreviation: α-NPD),4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation:TPD), 4,4′, 4″-tris(N, N-diphenyl-amino)-triphenylamine (abbreviation:TDATA), or 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine (abbreviation:MTDATA).

In addition, the hole transporting layer 112 may be a layer that has amultilayer structure formed by combining two or more layers eachincluding the material mentioned above.

Further, an electron transporting layer 114 may be provided between thesecond electrode 102 and the light-emitting layer 113 as shown inFIG. 1. Here, an electron transporting layer is a layer that has afunction of transporting electrons injected from the second electrode102 to the light-emitting layer 113. By providing the electrontransporting layer 114 to keep the second electrode 102 away from thelight-emitting element 113 in this way, quenching of emission due to ametal can be prevented.

The electron transporting layer 114 is not particularly limited, and itis possible to use a layer formed with the use of, for example, a metalcomplex including a quinoline skeleton or a benzoquinoline skeleton suchas tris(8-quinolinolato) aluminum (abbreviation: Alq₃),tris(4-methyl-8-quinolinolato) aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato) beryllium (abbreviation: BeBq₂), orbis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation:BAlq). In addition, a layer formed with the use of, for example, a metalcomplex including a oxazole-based ligand or a thiazole-based ligand suchas bis[2-(2-hydroxyphenyl)-benzoxazolato]zinc (abbreviation: Zn(BOX)₂)or bis[2-(2-hydroxyphenyl)-benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), may be used. Further, a layer formed with the use of2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene(abbreviation: to as OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproin (abbreviation: BCP) or the like may be used.

In addition, the electron transporting layer 114 may be a layer that hasa multilayer structure formed by combining two or more layers eachincluding the material mentioned above.

Further, a hole injecting layer may be provided between the firstelectrode 101 and the hole transporting layer 112 as shown in FIG. 1.Here, a hole injecting layer is a layer that has a function of assistinginjection of holes from an electrode to serve as an anode to the holetransporting layer 112. It is to be noted that injection of holes into alight-emitting layer may be assisted by providing a hole injecting layerbetween an electrode to serve as an anode and the light-emitting layerwhen no hole transporting layer is particularly provided.

The hole injecting layer 111 is not particularly limited, and it ispossible to use a layer formed with the use of, for example, a metaloxide such as molybdenum oxide (MoOx), vanadium oxide (VOx), rutheniumoxide (RuOx), tungsten oxide (WOx), manganese oxide (MnOx). In addition,the hole injecting layer 111 can be formed with the use of aphthalocyanine compound such as phthalocyanine (abbreviation: H₂Pc) orcopper phthalocyanine (abbreviation: CuPc), apoly(ethylenedioxythiophene)/poly(styrene sulfonate) aqueous solution(PEDOT/PSS), or the like.

Further, an electron injecting layer 115 may be provided between thesecond electrode 102 and the electron transporting layer 114 as shown inFIG. 1. Here, an electron injecting layer is a layer that has a functionof assisting injection of electrons from an electrode to serve as acathode to the electron transporting layer 114. It is to be noted thatinjection of electrons into a light-emitting layer may be assisted byproviding an electron injecting layer between an electrode to serve as acathode and the light-emitting layer when no electron transporting layeris particularly provided.

The electron injecting layer 115 is not particularly limited, it ispossible to used a layer formed with the use of, for example, a compoundof an alkali metal or an alkali-earth metal such as lithium fluoride(LiF), cesium fluoride (CsF), or calcium fluoride (CaF₂). In addition, alayer in which a highly electron-transporting material such as Alq₃ or4,4-bis(5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs) is mixedwith an alkali metal or an alkali-earth metal such as magnesium orlithium can also be used as the electron injecting layer 115.

In the above-described light-emitting element according to the presentinvention, each of the hole injecting layer 111, the hole transportinglayer 112, the light-emitting layer 113, the electron transporting layer114, and the electron injecting layer 115 may be formed by any onemethod of evaporation, inkjet, and coating. In addition, the firstelectrode 101 and the second electrode 102 may be formed by any onemethod of sputtering and evaporation.

Since the light-emitting element according to the present invention,which has a structure as described above, has the anthracene derivativeaccording to the present invention, the light-emitting element haslittle change in characteristics associated with change in properties ofa luminescent material due to repeated oxidation reactions, and showsstable light emission for a long period. In addition, since thelight-emitting element according to the present invention, which has astructure as described above, the anthracene derivative according to thepresent invention, the light-emitting element is able to emit lightefficiently.

Embodiment 3

The light-emitting element according to the present invention, which isdescribed in Embodiment 2, can be applied to a pixel portion of alight-emitting device that has a display function and a lighting portionof a light-emitting device that has a lighting function. Further, sincethe light-emitting element according to the present invention is capableof emitting light efficiently, a light-emitting device that is lower inpower consumption by using the light-emitting element according to thepresent invention. In addition, since the light-emitting elementaccording to the present invention has a long life, favorable displayimages or the like can be provided for a long period.

In the present embodiment, a circuit configuration and driving method ofa light-emitting device that has a display function will be describedwith reference to FIGS. 3 to 6.

FIG. 3 is an overhead schematic view of a light-emitting device to whichthe present invention is applied. In FIG. 3, a pixel portion 6511, asource signal line driver circuit 6512, a gate signal line drivercircuit 6513 for writing, and a gate signal line driver circuit 6514 forerasing are provided over a substrate 6500. Each of the source signalline driver circuit 6512, the gate signal line driver circuit 6513 forwriting, and the gate signal line driver circuit 6514 for erasing isconnected to FPC (Flexible Printed Circuit) 6503 that is an externalinput terminal through a group of wirings. Further, each of the sourcesignal line driver circuit 6512, the gate signal line driver circuit6513 for writing, and the gate signal line driver circuit 6514 forerasing receives signals such as a clock signal, a start signal, and areset signal from the FPC 6503. In addition, a printed wiring board(PWB) 6504 is attached to the FPC 6503. It is to be noted that it is notalways necessary to provide the driver circuit portion on the samesubstrate on which the pixel portion 6511 is provided as describedabove. For example, the driver circuit portion may be provided outsidethe substrate by using a TCP that has an IC chip on an FPC on which awiring pattern is formed.

In the pixel portion 6511, a plurality of source signal lines extendingin columns is arranged in rows, current supply lines are arranged inrows, and a plurality of gate signal lines extending in rows is arrangedin columns. Further, in the pixel portion 6511, a plurality of circuitseach including a light-emitting element is arranged.

FIG. 4 is a diagram showing a circuit for operating one pixel. Thecircuit shown in FIG. 4 includes a first transistor 901, a secondtransistor 902, and a light-emitting element 903.

Each of the first transistor 901 and the second transistor 902 is athree-terminal element including a gate electrode, a drain region, and asource region, and including a channel region between the drain regionand the source region. Here, since a source region and a drain regionare switched with each other in accordance with a structure or operatingconditions of a transistor, it is difficult to identify which one is thedrain region or the source region. Consequently, regions that serve as asource or a drain are referred to as first and second electrodes in thepresent embodiment.

A gate signal line 911 and a gate signal line driver circuit 913 forwriting are provided so as to be electrically connected or unconnectedby a switch 918, the gate signal line 911 and a gate signal line drivercircuit 914 for erasing are provided so as to be electrically connectedor unconnected by a switch 919, and a source signal line 912 is providedso as to be electrically connected to any one of a source signal linedriver circuit 915 and a power source 916 by a switch 920. Further, thefirst transistor 901 has a gate electrically connected to the gatesignal line 911, a first electrode electrically connected to the sourcesignal line 912, and a second electrode electrically connected to a gateelectrode of the second transistor 902. The second transistor 902 has afirst electrode electrically connected to a current supply line 917 anda second electrode electrically connected to one electrode included inthe light-emitting element 903. It is to be noted that the switch 918may be included in the gate signal line driver circuit 913 for writing,the switch 919 may be included in the gate signal line driver circuit914 for erasing, and the switch 920 may be included in the source signalline driver circuit 915.

In addition, arrangement of a transistor, a light-emitting element, andthe like is not particularly limited. For example, arrangement shown ina top view of FIG. 5 can be employed. In FIG. 5, a first transistor 1001has a first electrode connected to a source signal line 1004 and asecond electrode connected to a gate electrode of a second transistor1002. Further, the second transistor 1002 has a first electrodeconnected to a current supply line 1005 and a second electrode connectedan electrode 1006 of a light-emitting element. A portion of a gatesignal line 1003 serves as a gate electrode of the first transistor1001.

Next, a driving method will be described. FIG. 6 is a diagramillustrating operation per frame with time. In FIG. 6, the lateraldirection indicates passage of time, and the vertical directionindicates ordinal numbers of gate signal lines.

When a light-emitting device according to the present invention is usedto display images, rewrite operation and image display operation for ascreen are repeated in a display period. Although the number of rewritesis not particularly limited, it is preferable that the number ofrewrites be about 60 times per second so as not to make an image viewerrecognize flickers. Here, a period for which rewrite operation anddisplay operation are performed for a screen (one frame) is referred toas one frame period.

As shown in FIG. 6, one frame is divided (time division) into foursub-frames 501, 502, 503, and 504 respectively including writing periods501 a, 502 a, 503 a, and 504 a and retention periods 501 b, 502 b, 503b, and 504 b. In the retention period, a light-emitting element to whicha signal for emitting light is given is made to be in an emitting state.The ratio of the length of the retention period in each sub-frame isfirst sub-frame 501: second sub-frame 502: third sub-frame 503: fourthsub-frame 504=2³:2²:2¹:2⁰=8:4:2:1. This makes 4-bit gradation possible.However, the number of bits or the number of gradations is not limitedto that described here. For example, eight sub-frames may be provided soas to perform 8-bit gradation.

Operation in one frame will be described. First, in the sub-frame 501,writing operation is sequentially performed for each of the first row tothe last row. Accordingly, the start time of the writing period 501 a isdifferent depending on the row. When the writing period 501 a iscompleted, the row is sequentially moved into the retention period 501b. In the retention period 501 b, a light-emitting element to which asignal for emitting light is given is made to be in an emitting state.Further, when the retention period 501 b is completed, the row issequentially moved into the next sub-frame 502, and writing operation issequentially performed for each of the first row to the last row as inthe case of the sub-frame 501. The operation described above is repeatedto complete the retention period 504 b of the sub-frame 504. When theoperation in the sub-frame 504 is completed, the row is moved into thenext frame. Thus, the total of time for which light is emitted in eachsub-frame is emission time for each light-emitting element in one frame.By varying this emission time with respect to each light-emittingelement to have various combinations in one pixel, various differentdisplay colors in luminosity and chromaticity can be made.

As in the sub-frame 504, when forcible termination of a retention periodof a row for which writing is already completed to move into theretention time is required before writing for the last row is completed,it is preferable that an erasing period 504 c be provided after theretention period 504 b and a row be controlled so as to be in anon-emitting state forcibly. Further, the row made to be in thenon-emitting state forcibly is kept the non-emitting state for a certainperiod (this period is referred to as a non-emission period 504 d).Then, immediately after the writing period 504 a of the last row iscompleted, the rows are sequentially moved into the next writing period(or the next frame), starting from the first row. This makes it possibleto prevent the writing period 504 a of the sub-frame 504 fromoverlapping with the writing period of the next sub-frame.

Although the sub-frames 501 to 504 are arranged in the order ofretention period from longest to shortest in the present embodiment, thearrangement as in the present embodiment is not always necessary. Forexample, the sub-frames 501 to 504 may be arranged in the order ofretention period from shortest to longest, or may be arranged in randomorder. In addition, the sub-frames may be divided further into aplurality of frames. Namely, scanning of the gate signal lines may beperformed more than once while giving the same image signal.

Now, operation of the circuit shown in FIG. 4 in a writing period and anerasing period will be described.

First, operation in a writing period will be described. In the writingperiod, the n-th (n is a natural number) gate signal line 911 iselectrically connected to the gate signal line driver circuit 913 forwriting through the switch 918, and unconnected to the gate signal linedriver circuit 914 for erasing. In addition, the source signal line 912is electrically connected to the source signal line driver circuit 915through the switch 920. In this case, a signal is input to the gate ofthe first transistor 901 connected to the n-th (n is a natural number)gate signal line 911 to turn on the first transistor 901. Then, at thismoment, image signals are input simultaneously to the first to lastsource signal lines 912. It is to be noted that the image signals inputfrom the respective source signal lines 912 are independent of eachother. The image signal input from each of the source signal lines 912is input to the gate electrode of the second transistor 902 through thefirst transistor 901 connected to the source signal line 912. At thismoment, the value of current to be supplied from the current supply line917 to the light-emitting element 906 is determined in accordance withthe signal input to the second transistor 902. Then, depending on thevalue of the current, whether the light-emitting element 903 emits lightor not is determined. For example, when the second transistor 902 is ap-channel transistor, the light-emitting element 903 is made to emitlight by inputting a Low Level signal to the gate electrode of thesecond transistor 902. On the other hand, when the second transistor 902is an n-channel transistor, the light-emitting element 903 is made toemit light by inputting a High Level signal to the gate electrode of thesecond transistor 902.

Next, operation in an erasing period will be described. In the erasingperiod, the n-th (n is a natural number) gate signal line 911 iselectrically connected to the gate signal line driver circuit 914 forerasing through the switch 919. In addition, the source signal line 912is electrically connected to the power source 916 through the switch920. In this case, a signal is input to the gate of the first transistor901 connected to the n-th (n is a natural number) gate signal line 911to turn on the first transistor 901. Then, at this moment, erasingsignals are input simultaneously to the first to last source signallines 912. The erasing signal input from each of the source signal lines912 is input to the gate electrode of the second transistor 902 throughthe first transistor 901 connected to the source signal line 912. Atthis moment, current supply from the current supply line 917 to thelight-emitting element 903 is blocked in accordance with the signalinput to the second transistor 902. Then, the light-emitting element 903is forcibly made to be in a non-emitting state. For example, when thesecond transistor 902 is a p-channel transistor, the light-emittingelement 903 is made to emit no light by inputting a High Level signal tothe gate electrode of the second transistor 902. On the other hand, whenthe second transistor 902 is an n-channel transistor, the light-emittingelement 903 is made to emit no light by inputting a Low Level signal tothe gate electrode of the second transistor 902.

It is to be noted that, as for the n-th row (n is a natural number),signals for erasing are input by the operation as described above in anerasing period. However, as described above, the other row (referred toas the m-th row (m is a natural number)) may be in a writing periodwhile the n-th row is in an erasing period. In such a case, it isnecessary to input a signal for erasing to the n-th row and input asignal for writing to the m-th row by using the same source signal line.Therefore, operation described below is preferable.

Immediately after the n-th light-emitting element 903 is made to emit nolight by the operation in the erasing period described above, the gatesignal line 911 and the gate signal line driver circuit 914 for erasingare made to be unconnected to each other, and the switch 920 is switchedto connect the source signal line 912 and the source is signal linedriver circuit 915. Then, in addition to connecting the source signalline 912 to the source signal line driver circuit 915, the gate signalline 911 is connected to the gate signal line driver circuit 913 forwriting. Then, a signal is input selectively to the m-th gate signalline 911 from the gate signal line driver circuit 913 for writing toturn on the first transistor 901, and signals for writing are input tothe first to last source signal lines 912 from the source signal linedriver circuit 915. This signal makes the m-th light-emitting element903 is made to be in an emitting or non-emitting state.

Immediately after the writing period for the m-th row is completed asdescribed above, an erasing period for the (n+1)-th row is started. Forthat purpose, the gate signal line 911 and the gate signal line drivercircuit 913 for writing are made to be unconnected to each other, andthe switch 920 is switched to connect the source signal line 912 and thepower source 916. Further, the gate signal line 911, which isunconnected to the gate signal line driver circuit 913 for writing, ismade to be connected to the gate signal line driver circuit 914 forerasing. Then, a signal is input selectively to the (n+1)-th gate signalline 911 from the gate signal line driver circuit 914 for erasing toturn on the first transistor 901, and an erasing signal is input fromthe power source 906. Immediately after the erasing period for the(n+1)-th row is completed, a writing period for the (m+1)-th row isstarted. Then, an erasing period and a writing period may be repeated inthe same way until an erasing period for the last row is completed.

Although the example in which the writing period for the m-th row isprovided between the erasing period for the n-th row and the erasingperiod for the (n+1)-th row is described in the present embodiment, thepresent invention is not limited to this. The writing period for them-th row may be provided between an erasing period for (n−1)-th row andan erasing period for n-th row.

In addition, in the present embodiment, the operation in which the gatesignal line driver circuit 914 for erasing and one gate signal line 911are made to be unconnected to each other and the gate signal line drivercircuit 913 for writing the other gate signal line 911 are made to beconnected to each other is repeated as the non-emission period 504 d isprovided in the sub-frame 504. This type of operation may be performedin a frame in which a non-emission period is not provided.

Embodiment 4

One example of a cross-sectional view of a light-emitting deviceincluding a light-emitting element according to the present inventionwill be described with reference to FIGS. 7A to 7C.

In each of FIGS. 7A to 7C, a portion surrounded by a dotted line is atransistor 11 provided for driving a light-emitting element 12 accordingto the present invention. The light-emitting element 12 is alight-emitting element according to the present invention, which has alight-emitting layer 15 between a first electrode 13 and a secondelectrode 14. The first electrode 13 and a drain of the transistor 11are electrically connected to each other by a wiring 17 running througha first interlayer insulating film 16 (16 a to 16 c). In addition, thelight-emitting element 12 is separated by a partition layer 18 fromanother light-emitting element provided adjacently. A light-emittingdevice that has this structure according to the present invention isprovided over substrate 10.

The transistor 11 shown in each of FIGS. 7A to 7C is a top-gate TFT inwhich a gate electrode is provided over a semiconductor layer with agate insulating film interposed therebetween. However, the structure ofthe transistor 11 is not particularly limited. For example, abottom-gate TFT may be used. In the case of a bottom-gate TFT, a TFTwhere a protective film is formed on a semiconductor layer that forms achannel (a channel-protection TFT) may be used, or a TFT where a portionof a semiconductor layer that forms a channel is concave (a channel-etchTFT) may be used. Here, reference numerals 21, 22, 23, 24, 25, and 26denote a gate electrode, a gate insulating film, a semiconductor layer,an n-type semiconductor layer, an electrode, and a protective film,respectively.

In addition, a semiconductor layer forming the transistor 11 may beeither crystalline or amorphous, or alternatively, may besemi-amorphous.

The following will describe a semi-amorphous semiconductor. Thesemi-amorphous semiconductor is a semiconductor that has an intermediatestructure between amorphous and crystalline (such as single-crystal orpolycrystalline) structures and has a third state that is stable interms of free energy, which includes a crystalline region that has shortrange order and lattice distortion. Further, a crystal grain from 0.5 to20 nm is included in at least a region in a film of the semi-amorphoussemiconductor. A raman spectrum of the semi-amorphous semiconductor hasa shift to a lower wavenumber side than 520 cm⁻¹. In X-ray diffraction,diffraction peaks of (111) and (220) due to a Si crystal lattice areobserved. Hydrogen or halogen is included at 1 atomic % or more in thesemi-amorphous semiconductor to terminate a dangling bond. Therefore,the semi-amorphous semiconductor is also referred to as amicro-crystalline semiconductor. A nitride gas is decomposed by glowdischarge (plasma CVD) to form the semi-amorphous semiconductor. As thenitride gas, in addition to SiH₄, a gas such as Si₂H₆, SiH₂Cl₂, SiHCl₃,SiCl₄, or SiF₄ can be used. This nitride gas may be diluted with H₂ orwith H₂ and one kind or plural kinds of rare gas elements selected fromHe, Ar, Kr, and Ne, where the dilution ratio is in the range of 2:1 to1000:1. The pressure during glow discharge is approximately in the rangeof 0.1 Pa to 133 Pa, and the power supply frequency is in the range of 1MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heatingtemperature may be 300° C. or less, preferably 100 to 250° C. It isdesirable to control an impurity of an atmospheric constituent such asoxygen, nitrogen, or carbon to have a concentration of 1×10²⁰/cm³ orless as an impurity element in the film, in particular, the oxygenconcentration is controlled to be 5×10¹⁹/cm³ or less, preferably1×10¹⁹/cm³ or less.

Further, specific examples of crystalline semiconductors for thesemiconductor layer include single-crystal or polycrystalline siliconand silicon-germanium, which may be formed by laser crystallization ormay be formed by crystallization with solid-phase growth using anelement such as nickel.

In the case of using an amorphous material, for example, amorphoussilicon to form the semiconductor layer, it is preferable that thelight-emitting device have a circuit in which the transistor 11 and theother transistor (a transistor forming the circuit for driving thelight-emitting element) are all n-channel transistors. Other than thatcase, the light-emitting device may have a circuit including one of ann-channel transistor and a p-channel transistor or may have a circuitincluding both an n-channel transistor and a p-channel transistor.

Further, the first interlayer insulating film 16 may be a multilayer asshown in FIGS. 7A and 7C, or may be a single layer. The first interlayerinsulating film 16 a includes an inorganic material such as siliconoxide or silicon nitride, and the first interlayer insulating film 16 bincludes a material with self-flatness such as acrylic, siloxane (amaterial that has a framework structure formed by the bond betweensilicon (Si) and oxygen (O) and includes at least hydrogen in asubstituent), silicon oxide that can be used in coating deposition. Inaddition, the first interlayer insulating film 16 c has a siliconnitride film including argon (Ar). The materials included in therespective layers are not particularly limited, and therefore materialsother than the materials mentioned here may be used. Further, a layerincluding a material other than these materials may be combined. In thisway, both of an inorganic material and an organic material, or one of aninorganic material and an organic material may be used to form the firstinterlayer insulating film 16.

As for the partition layer 18, it is preferable that an edge portionhave a shape varying continuously in curvature radius. In addition, amaterial such as acrylic, siloxane, resist, or silicon oxide is used toform the partition layer 18. One or both of an inorganic material and anorganic material may be used to form the partition layer 18.

In each of FIGS. 7A and 7C, only the first interlayer insulating film 16is provided between the transistor 11 and the light-emitting element 12.However, as shown in FIG. 7B, a second interlayer insulating film 19 (19a and 19 b) may be provided in addition to the first interlayerinsulating film 16 (16 a and 16 b). In the light-emitting device shownin FIG. 7B, the first electrode 13 is connected to the wiring 17 throughthe second interlayer insulating film 19.

The second interlayer insulating film 19 may be a multilayer or a singlelayer in the same way as the first interlayer insulating film 16. Thesecond interlayer insulating film 19 a includes a material withself-flatness such as acrylic, siloxane (a material that has a frameworkstructure formed by the bond between silicon (Si) and oxygen (O) andincludes at least hydrogen in a substituent), silicon oxide that can beused in coating deposition. In addition, the second interlayerinsulating film 19 b has a silicon nitride film including argon (Ar).The materials included in the respective layers are not particularlylimited, and therefore materials other than the materials mentioned heremay be used. Further, a layer including a material other than thesematerials may be combined. In this way, both of an inorganic materialand an organic material, or one of an inorganic material and an organicmaterial may be used to form the second interlayer insulating film 19.

In the light-emitting element 12, in the case where both of the firstelectrode 13 and the second electrode 14 are formed by using alight-transmitting material, emitted light can be extracted from boththe first electrode 13 side and the second electrode 14 side asindicated by outline arrows of FIG. 7A. In the case where only thesecond electrode 14 is formed by using a light-transmitting material,emitted light can be extracted from only the second electrode 14 side asindicated by an outline arrow of FIG. 7B. In this case, it is preferablethat the first electrode 13 include a highly reflective material or thata film composed of a highly reflective material (a reflective film) beprovided below the first electrode 13. In the case where only the firstelectrode 13 is formed by using a light-transmitting material, emittedlight can be extracted from only the first electrode 13 side asindicated by an outline arrow of FIG. 7C. In this case, it is preferablethat the second electrode 14 include a highly reflective material orthat a reflective film is provided above the second electrode 14.

In addition, in the case of the light-emitting element 12, the firstelectrode 13 may function as an anode while the second electrode 14functions as a cathode, or alternatively, the first electrode 13 mayfunction as a cathode while the second electrode 14 functions as ananode. However, the transistor 11 is a p-channel transistor in theformer case, and the transistor 11 is an n-channel transistor in thelatter case.

Embodiment 5

By mounting a light-emitting device according to the present invention,an electronic device that is capable of favorable displays for a longperiod or an electric is appliance that is capable of favorable lightingfor a long period can be obtained.

FIGS. 8A to 8C show examples of an electronic device mounted with alight-emitting device to which the present invention is applied.

FIG. 8A shows a laptop personal computer manufactured according to thepresent invention, which includes a main body 5521, a frame body 5522, adisplay portion 5523, and a keyboard 5524. The personal computer can becompleted by incorporating a light-emitting device that has alight-emitting element according to the present invention in the displayportion 5523.

FIG. 8B shows a cellular phone manufactured according to the presentinvention, which includes a main body 5552, a display portion 5551, avoice output portion 5554, a voice input portion 5555, operation keys5556 and 5557, and an antenna 5553. The cellular phone can be completedby incorporating a light-emitting device that has a light-emittingelement according to the present invention into the display portion5551.

FIG. 8C shows a television manufactured according to the presentinvention, which includes a display portion 5531, a frame body 5532, anda speaker 5533. The television can be completed by incorporating alight-emitting device that has a light-emitting element according to thepresent invention into the display portion 5531.

As described above, a light-emitting device according to the presentinvention is suitable for use as display portions of various electronicdevices.

In the present embodiment, the laptop personal computer, the cellularphone, and the television are described. However, in addition, alight-emitting device that has a light-emitting element according to thepresent invention may be mounted in devices such as a car navigationsystem and a lighting apparatus.

Example 1 Synthesis Example [Step 1]

A synthesis method of 9,10-bis(4-bromophenyl)-2-tert-butylanthracenewill be described.

Under a nitrogen flow, at −78° C., a 1.58 N hexane solution ofbutyllithium (13.4 mL) was dropped in a dry ether solution (200 mL) ofp-dibromobenzene (5.0 g). After completion of the dropping, stirring wascarried out at the same temperature (−78° C.). A dry ether solution (40mL) of 2-t-butylanthraquinone (2.80 g) was dropped at −78° C., and thenthe reaction solution was slowly raised to room temperature. Afterovernight stirring at room temperature, water was added, and extractionwas carried out with ethyl acetate. The organic layer was washed with asaturated aqueous solution of sodium chloride, dried with magnesiumsulfate, filtered, and condensed. Then, the residue was purified bysilica gel chromatography (developing solvent, hexane-ethyl acetate) toobtain a compound (5.5 g).

Measurement of the obtained compound by nuclear magnetic resonance(¹H-NMR) could confirm that the compound was9,10-bis(4-bromophenyl)-2-tert-butyl-9,10-dihydroxy-9,10-dihydroanthracene.

¹H-NMR data of this compound is shown below.

¹H-NMR (300 MHz, CDCl₃); δ=1.31 (s, 9H), 2.81 (s, 1H), 2.86 (s, 1H),6.82-6.86 (m, 4H), 7.13-7.16 (m, 4H), 7.36-7.43 (m, 3H), 7.53-7.70 (m,4H)

In addition, the synthesis scheme (b-1) of9,10-bis(4-bromophenyl)-2-tert-butyl-9,10-dihydroxy-9,10-dihydroanthraceneis shown below.

In the atmosphere, 987 mg (1.55 mmol) of the thus synthesized9,10-bis(4-bromophenyl)-2-tert-butyl-9,10-dihydroxy-9,10-dihydroanthracene,664 mg (4 mmol) of potassium iodide, and 1.48 g (14 mmol) of sodiumphosphinate dehydrate were suspended in 14 mL of glacial acetic acid,and held at reflux for 2 hours while heating and stirring. After coolingto room temperature, a produced precipitation was filtered, and washedwith about 50 mL of methanol to obtain a filtered object. Then, thefiltered object was dried to obtain a cream powdery compound (700 mg).The yield was 82%. Measurement of this compound by nuclear magneticresonance (¹H-NMR and ¹³C-NMR) could confirm that the compound was9,10-bis(4-bromophenyl)-2-tert-butylanthracene.

¹H-NMR data and ¹³C-NMR data of this compound is shown below.

¹H-NMR (300 MHz, CDCl₃); δ=1.28 (s, 9H), 7.25-7.37 (m, 6H), 7.44-7.48(m, 1H), 7.56-7.65 (m, 4H), 7.71-7.76 (m, 4H)

¹³C-NMR (74 MHz, CDCl₃); δ=30.8, 35.0, 120.8, 121.7, 121.7, 124.9,125.0, 125.2, 126.4, 126.6, 126.6, 128.3, 129.4, 129.7, 129.9, 131.6,131.6, 133.0, 133.0, 135.5, 135.7, 138.0, 138.1, 147.8

In addition, the synthesis scheme (b-2) of9,10-bis(4-bromophenyl)-2-tert-butylanthracene is shown below.

[Step 2]

A synthesis method of N-(4-diphenylamino)phenylalanine will bedescribed.

In a 1000 mL erlenmayer flask, 25.19 g (0.102 mol) of triphenylamine,18.05 g (0.102 mol) of N-bromosuccinimide, and 400 mL of ethyl acetatewere put, and stirred at room temperature in the air for about 12 hours.After completion of the reaction, the organic layer was washed twicewith a saturated aqueous solution of sodium carbonate, then, the aqueouslayer was subjected to extraction twice with ethyl acetate, and theethyl acetate layer mixed with the organic layer was washed with asaturated aqueous solution of sodium chloride. After drying withmagnesium sulfate, natural filtration, and condensation, the obtainedcolorless solid was recrystallized with ethyl acetate and hexane toobtain a colorless powdery solid (22.01 g, yield: 66%). Nuclear magneticresonance (¹H-NMR) could confirm that this colorless powdery solid was4-bromotriphenylamine. The measurement result by nuclear magneticresonance (NMR) is shown below.

¹H-NMR data of this compound is shown below.

-   -   ¹H-NMR (300 MHz, CDCl₃) δ ppm: 7.32 (d, 2H, J=8.7 Hz), 7.29-7.23        (m, 4H), 7.08-7.00 (m, 6H), 6.94 (d, 2H, J=8.7 Hz)

In addition, the synthesis scheme (c-1) of 4-bromotriphenylamine isshown below.

Next, 7.21 g (0.053 mol) of acetoanilide, 17.32 g (0.053 mol) of thesynthesized 4-bromotriphenylamine, 2.05 g (0.011 mol) of copper (I)iodide, and 22.00 g (0.103 mol) of tripotassium phosphate were put in a500 mL three-neck flask, and the atmosphere in the flask was made anitrogen atmosphere. Then, 150 mL of dioxane and 1.3 mL oftrans-1,2-cyclohexanediamine were added, and reflux for 40 hours wascarried out. After completion of the reaction, the solid in the flaskwas removed by suction filtration after cooling to room temperature. Thefiltrate was washed twice with a saturated aqueous solution of sodiumcarbonate, the aqueous layer was subjected to extraction twice withchloroform, and the chloroformlayer mixed with the organic layer waswashed with a saturated aqueous solution of sodium chloride. Afterdrying with magnesium sulfate, natural filtration, and condensation, theobtained white solid was purified by silica gel chromatography (ethylacetate:hexane=1:1) to obtain a white powdery solid (12.00 g, yield:59%). Nuclear magnetic resonance (¹H-NMR) could confirm that this whitepowdery solid was N-(4-diphenylamino) phenylacetoanilide.

¹H-NMR data of this compound is shown below.

¹H-NMR (300 MHz, CDCl₃) δ ppm: 7.36-7.23 (m, 9H), 7.12-7.03 (m, 10H),2.07 (s, 3H)

In addition, the synthesis scheme (c-2) of N-(4-diphenylamino)phenylacetoanilide is shown below.

In a 500 mL recovery flask, 20.00 g (0.053 mol) of the synthesizedN-(4-diphenylamino)phenylacetoanilide, 100 g of a 40% sodium hydroxidesolution, 50 mL of tetrahydrofuran, and 50 mL of ethanol were put, andreflux was carried out for 2 hours in the air. After completion of thereaction, the sodium hydroxide solution was removed after cooling toroom temperature. The organic layer was washed twice with water, theaqueous layer was subjected to extraction twice with chloroform, and thechloroformlayer mixed with the organic layer was washed with a saturatedaqueous solution of sodium chloride. After drying with magnesiumsulfate, natural filtration, and condensation, the obtained colorlesssolid was recrystallized with ethyl acetate and hexane to obtain acolorless powdery solid (14.69 g, yield: 83%). Nuclear magneticresonance (¹H-NMR) could confirm that this colorless powdery solid wasN-(4-diphenylamino)phenylalanine.

¹H-NMR data of this compound is shown below.

¹H-NMR (300 MHz, CDCl₃) δ ppm: 7.30-7.20 (m, 5H), 7.08-6.87 (m, 14H),5.61 (s, 1H)

In addition, the synthesis scheme (c-3) of N-(4-diphenylamino)phenylalanine is shown below.

[Step 3]

A synthesis method of9,10-bis{4-[N-(4-diphenylamino)phenyl-N-phenyl]aminophenyl}-2-tert-butylanthracenerepresented by the structure formula (6) will be described.

In a 200 mL three-neck flask, 2.00 g (0.0037 mol) of9,10-bis(4-bromophenyl)-2-tert-butylanthracene, 2.61 g (0.0078 mol) ofN-(4-diphenylamino)phenylalanine, 428 mg (0.77 mmol) ofbis(dibenzylideneacetone)palladium(0), and 2.00 g (0.021 mol) of sodiumt-butoxide were put, and the atmosphere within the flask was made to beunder a nitrogen flow. After that, 20 mL of dehydrated toluene and 4.0mL of a 10% hexane solution of tri-tert-butylphosphine were added, andstirring was carried out at 80° C. for 8 hours. After completion of thereaction, the reaction solution was cooled to room temperature andwashed twice with water, the aqueous layer was subjected to extractiontwice with chloroform, and the chloroformlayer mixed with the organiclayer was washed with a saturated aqueous solution of sodium chlorideand dried with magnesium sulfate. After natural filtration andcondensation, the obtained brown oily object was purified by silica gelchromatography (hexane:ethyl acetate=9:1) and then recrystallized withethyl acetate and hexane to obtain a yellow powdery solid (1.14 g,yield: 29%, refer to a synthesis scheme (d-1)). Nuclear magneticresonance (¹H-NMR) could confirm that this yellow powdery solid was9,10-bis{4-[N-(4-diphenylamino)phenyl-N-phenyl]aminophenyl}-2-tert-butylanthracene(abbreviation: DPABPA).

¹H-NMR data of this compound is shown below.

¹H-NMR (300 MHz, CDCl₃) δ ppm: 7.89-7.81 (m, 2H), 7.78 (d, 1H, J=9.3Hz), 7.66 (d, 2H, J=1.8 Hz), 7.48 (d, d, 1H, J=9.3 Hz), 7.38-7.24 (m,25H), 7.17-7.13 (m, 12H), 7.08-6.98 (m, 10H), 1.30 (s, 9H)

In addition, the synthesis scheme (d-1) of DPABPA is shown below.

Further, FIG. 9 shows an absorption spectrum of a single film of DPABPA.In FIG. 9, the horizontal axis indicates a wavelength (nm), and thevertical axis indicates an absorbance (without a unit). In addition,FIG. 10 shows an emission spectrum of the single film of DPABPA excitedat 403 nm. In FIG. 10, the horizontal axis indicates a wavelength (nm),and the vertical axis indicates emission intensity (arbitrary unit).From FIG. 10, it is determined that the single film of DPABPA shows blueor bluish luminescence with a peak at 494 nm.

Further, the stability of DPABPA against oxidation was examined bycyclic voltammetry (CV). It is to be noted that an electrochemicalanalyzer (ALS, Model 600A) from BAS was used for the measurement.

In the CV measurement, tetra-n-butylammonium perchlorate (n-Bu₄NClO₄)and dimethylformamide (DNF) were used as a supporting electrolyte and asolvent, respectively. In addition, a Pt electrode, a Pt electrode, anda Ag/Ag⁺ electrode were used as a work electrode, an auxiliaryelectrode, and a reference electrode, respectively. The scan rate in theCV measurement is controlled to be 0.025 V/s, and a series of operationsas one cycle, scanning for changing the potential of the work electrodewith respect to the Ag/Ag⁺ from 0 to 0.4 V and scanning for returningthe potential from 0.4 to 0 V, was performed repeatedly to complete 500cycles.

The result is shown in FIG. 11. It is to be noted that the horizontalaxis and the vertical axis respectively indicate a potential (V) withrespect to the Ag/Ag⁺ electrode and a current value (A) in FIG. 11. FromFIG. 11, it is determined that the oxidation potential is 24 V (vs.Ag/Ag⁺ electrode). In addition, there is almost no variation in peakposition or peak intensity of the CV curve in FIG. 11 in spite of therepeated 500 cycles of operations. From this result, it is determinedthat DPABPA according to the present invention is quite stable againstoxidation.

Example 2

In the present example, an example of manufacturing a light-emittingelement using9,10-bis[4-(N-(4-diphenylamino)phenyl-N-phenyl)aminophenyl]-2-tert-butylanthracene(abbreviation: DPABPA) represented by the structure formula (6) will bedescribed with reference to FIG. 2.

On a glass substrate 701, indium tin oxide containing silicon wasdeposited by sputtering to form a first electrode 702. The filmthickness thereof was made to be 110 nm.

Next, on the first electrode 702, DNTPD was deposited by vacuumevaporation to form a layer 703 including DNTPD. The film thicknessthereof was made to be 30 nm.

Next, on the layer 703 including DNTPD, α-NPD was deposited by vacuumevaporation to form a layer 704 including α-NPD. The film thicknessthereof was made to be 30 nm.

Next, on the layer 704 including A-NPD, t-BuDNA and DPABPA representedby the structure formula (6) were deposited by co-evaporation to form alayer 705 including t-BuDNA and DPABPA. The layer 705 was made toinclude t-BuDNA at 95 weight % and DPABPA at 5 weight %. This makesDPABPA dispersed as guest material in t-BuDNA as host material. Inaddition, the film thickness of the layer 705 was made to be 40 nm. Itis to be noted that co-evaporation is an evaporation method in whichevaporation is performed simultaneously from a plurality of evaporationsources.

Next, on the layer 705 including t-BuDNA and DPABPA, Alq₃ was depositedby vacuum evaporation to form a layer 706 including Alq₃. The filmthickness thereof was made to be 20 nm.

Next, on the layer 706 including Alq₃, calcium fluoride was deposited byvacuum evaporation to form a layer 707 including calcium fluoride. Thefilm thickness thereof was made to be 1 nm.

Next, on the layer 707 including calcium fluoride, aluminum wasdeposited by vacuum evaporation to form a second electrode 708.

By manufacturing a light-emitting element as described above, it ispossible to obtain a light-emitting element from which luminescence fromDPABPA can be obtained.

In the thus manufactured light-emitting element, when a voltage isapplied to the first electrode 702 and the second electrode 708 to flowcurrent, DPABPA produces luminescence. In this case, the first electrode702 serves as an anode and the second electrode 708 serves as a cathode.In addition, the layer 703 including DNTPD, the layer 704 includingα-NPD, the layer 705 including t-BuDNA and DPABPA, the layer 706including Alq₃, and the 707 including calcium fluoride serve as a holeinjecting layer, a hole transporting layer, a light-emitting layer, anelectron transporting layer, and an electron injecting layer,respectively.

Further, sealing of the light-emitting element manufactured as describedabove was performed. It is to be noted that the sealing was performed ina nitrogen atmosphere in a glove box.

Then, the light-emitting element after the sealing was driven to examinecurrent density-luminance characteristics, voltage-luminancecharacteristics, and luminance-current efficiency characteristics in aninitial condition. It is to be noted that the measurement was performedin an atmosphere kept at 25° C.

FIGS. 12, 13, 14 respectively show current density-luminancecharacteristics, voltage-luminance characteristics, andluminance-current efficiency characteristics. In FIG. 12, the horizontalaxis indicates a current density, and the vertical axis indicates aluminance. In FIG. 13, the horizontal axis indicates a voltage, and thevertical axis indicates a luminance. In FIG. 14, the horizontal axisindicates a luminance, and the vertical axis indicates a currentefficiency.

From the voltage-luminance characteristics in FIG. 13, it is determinedthat the light-emitting element in the present example emitted lightwith a luminance of 290 cd/m² when a voltage of 6.6 V was applied. Inaddition, it is determined that the luminance efficiency was 8.2 cd/Awhen the voltage of 6.6 V was applied.

Further, an emission spectrum of the light-emitting element had a peakat 486 nm, and the CIE chromaticity coordinates were (x, y)=(0.19,0.37).

For the light-emitting element in the present invention, which has theinitial performance described above, an operational stability test byconstant current driving was performed. A current of a current density(3.54 mA/cm²) required for emitting light with a luminance of 290 cd/m²in the initial condition was kept flowed for a certain period of time toexamine change in luminance with time. In the result, it was determinedthat the luminance after a lapse of 600 hours was 86% of the luminancein the initial condition. From this result, it is determined that thelight-emitting element according to the present invention is smallreduced in luminance with time, and has a favorable life.

FIG. 15 shows the measurement result of the operational stability test.In FIG. 15, the horizontal axis indicates elapsed time (hour) since theinitial state, and the vertical axis indicates a relative luminance(arbitrary unit) with respect to the initial luminance when the initialluminance is indicated as 100.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless such changes andmodifications depart from the scope of the present invention hereinafterdefined, they should be construed as being included therein.

1. A lighting apparatus having a light-emitting element, the light-emitting element comprises an anthracene derivative represented by a general formula (1),

wherein R² and R⁷ are a group represented by a structure formula (2), and R¹, R³ to R⁵, R⁶, and R⁸ to R¹⁰ are individually any one of hydrogen and an alkyl group having 1 to 4 carbon atoms


2. A lighting apparatus having a light-emitting element, the light-emitting element comprises an anthracene derivative represented by a general formula (3),

wherein R¹¹, R¹³, R¹⁶, and R¹⁸ are an alkyl group having 1 to 4 carbon atoms, and R¹², R¹⁴, R¹⁵, and R¹⁷ are individually any one of hydrogen and an alkyl group having 1 to 4 carbon atoms.
 3. A lighting apparatus having a light-emitting element, the light-emitting element comprises an anthracene derivative represented by a general formula (4),

wherein R²¹ to R²⁸ are individually any one of hydrogen and an alkyl group having 1 to 4 carbon atoms, and R²¹ and R²², R²² and R²³, R²⁵ and R²⁶, and R²⁶ and R²⁷ may be individually bonded to form an aromatic ring.
 4. A lighting apparatus having a light-emitting element, the light-emitting element comprises an anthracene derivative represented by a general formula (5),

wherein Ar¹ and Ar² are individually an aryl group having 10 to 14 carbon atoms.
 5. The lighting apparatus according to claim 1, wherein the light-emitting element comprises a light-emitting layer in which the anthracene derivative is incorporated.
 6. The lighting apparatus according to claim 1, wherein the light-emitting element comprises a light-emitting layer comprising a substance whose energy gap is larger than that of the anthracene derivative, and wherein the anthracene derivative is doped in the light-emitting layer.
 7. The lighting apparatus according to claim 1, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, and wherein the light-emitting layer comprises the anthracene derivative.
 8. The lighting apparatus according to claim 1, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, wherein the light-emitting layer comprises the anthracene derivative, and wherein the metal oxide is selected from molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide.
 9. The lighting apparatus according to claim 2, wherein the light-emitting element comprises a light-emitting layer in which the anthracene derivative is incorporated.
 10. The lighting apparatus according to claim 2, wherein the light-emitting element comprises a light-emitting layer comprising a substance whose energy gap is larger than that of the anthracene derivative, and wherein the anthracene derivative is doped in the light-emitting layer.
 11. The lighting apparatus according to claim 2, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, and wherein the light-emitting layer comprises the anthracene derivative.
 12. The lighting apparatus according to claim 2, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, wherein the light-emitting layer comprises the anthracene derivative, and wherein the metal oxide is selected from molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide.
 13. The lighting apparatus according to claim 3, wherein the light-emitting element comprises a light-emitting layer in which the anthracene derivative is incorporated.
 14. The lighting apparatus according to claim 3, wherein the light-emitting element comprises a light-emitting layer comprising a substance whose energy gap is larger than that of the anthracene derivative, and wherein the anthracene derivative is doped in the light-emitting layer.
 15. The lighting apparatus according to claim 3, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, and wherein the light-emitting layer comprises the anthracene derivative.
 16. The lighting apparatus according to claim 3, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, wherein the light-emitting layer comprises the anthracene derivative, and wherein the metal oxide is selected from molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide.
 17. The lighting apparatus according to claim 4, wherein the light-emitting element comprises a light-emitting layer in which the anthracene derivative is incorporated.
 18. The lighting apparatus according to claim 4, wherein the light-emitting element comprises a light-emitting layer comprising a substance whose energy gap is larger than that of the anthracene derivative, and wherein the anthracene derivative is doped in the light-emitting layer.
 19. The lighting apparatus according to claim 4, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, and wherein the light-emitting layer comprises the anthracene derivative.
 20. The lighting apparatus according to claim 4, wherein the light-emitting element comprises a light-emitting layer and a hole-injection layer which are interposed between an anode and a cathode, wherein the hole-injection layer comprises a metal oxide and is in contact with the anode, wherein the light-emitting layer comprises the anthracene derivative, and wherein the metal oxide is selected from molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide. 